JS3
When you complete your CPL application form you are asked whether you want the CPL issued for s/e aircraft or m/e aircraft.
You can tick both boxes if you want it issued against both ratings. The CAA may, or may not, charge you an extra £100 if you want it issued against both.
You will have an SEP class rating by virtue of the fact that you have done a s/e CPL.
You will have to do a JAA MEP test to convert your non-JAA MEP to a JAA one. This should be done before your IR skill test.
Linda